8-Lead, Low-Cost, System
Temperature Monitor
a
ADM1020
FEATURES
PRODUCT DESCRIPTION
On-Chip and Remote Temperature Sensing
No Calibration Necessary
The ADM1020 is a two-channel digital thermometer and
under/over temperature alarm, intended for use in personal
computers and other systems requiring thermal monitoring and
management. The device can measure the temperature of a
microprocessor using a diode-connected NPN or PNP transis-
tor, which may be provided on-chip in the case of the Pentium®
II or similar processors, or can be a low-cost discrete device
such as the 2N3904. A novel measurement technique cancels
out the absolute value of the transistor’s base emitter voltage, so
that no calibration is required. The second measurement chan-
nel measures the output of an on-chip temperature sensor, to
monitor the temperature of the device and its environment.
1؇C Accuracy for On-Chip Sensor
3؇C Accuracy for Remote Sensor
Programmable Over/Under Temperature Limits
Programmable Conversion Rate
2-Wire SMBus™ Serial Interface
Supports SMBus Alert
70 A Max Operating Current
3 A Standby Current
+3 V to +5.5 V Supply
8-Lead SOIC Package
The ADM1020 communicates over a two-wire serial interface
compatible with System Management Bus (SMBus) standards.
Under and over temperature limits can be programmed into the
devices over the serial bus, and an ALERT output signals when
the on-chip or remote temperature is out of range. This output
can be used as an interrupt, or as an SMBus alert.
APPLICATIONS
Desktop Computers
Notebook Computers
Smart Batteries
Industrial Controllers
Telecommunication Equipment
Instrumentation
FUNCTIONAL BLOCK DIAGRAM
ADDRESS POINTER
REGISTER
ONE-SHOT
REGISTER
CONVERSION RATE
REGISTER
LOCAL TEMPERATURE
VALUE REGISTER
LOCAL TEMPERATURE
LOW LIMIT COMPARATOR
LOCAL TEMPERATURE
LOW LIMIT REGISTER
ON-CHIP TEMP.
SENSOR
LOCAL TEMPERATURE
HIGH LIMIT COMPARATOR
LOCAL TEMPERATURE
HIGH LIMIT REGISTER
D+
D–
ANALOG
MUX
8-BIT A-TO-D
CONVERTER
REMOTE TEMPERATURE
LOW LIMIT COMPARATOR
REMOTE TEMPERATURE
LOW LIMIT REGISTER
RUN/STANDBY
BUSY
REMOTE TEMPERATURE
VALUE REGISTER
REMOTE TEMPERATURE
HIGH LIMIT COMPARATOR
REMOTE TEMPERATURE
HIGH LIMIT REGISTER
CONFIGURATION
REGISTER
EXTERNAL DIODE OPEN-CIRCUIT
INTERRUPT
MASKING
ALERT
STATUS REGISTER
ADM1020
SMBUS INTERFACE
V
GND
SDATA
SCLK
ADD
DD
SMBus is a trademark of Intel Corporation.
Pentium is a registered trademark of Intel Corporation.
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
Fax: 781/326-8703
World Wide Web Site: http://www.analog.com
© Analog Devices, Inc., 1999